Sending system



May 11,1926. 1,584,561

L. KUHN I SENDING SYSTEM Filed Sept. .5 1921 Patented May 11, 1926,

UNITED STATES PATENT OFFICE.

LUDWIG xttrm, or cmarorrnuaune, um BERLIN, REPUBLIC or GERMANY, as

SIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, OF EASTPITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

. SENDING sysrnm,

Application filed September 3, 1921. Serial No. 498,566.

' (GRANTED UNDER THE PROVISIONS 01? THE ACT OF MARCH 3, 1921, 41 STAT.L, 1318.)

This invention relates to sending devices for either telegraphic ortelephonic radio communication.

It is an object of this invention to avoid the disadvantageswhich'frequently accompany the regenerative action of transm tters inwhich the plate circuit is eleotrosta ically or electromagneticallycoupled to the grid circuit. o

fIt'is a further object of this invention to provide for modifying theamplitude'of of the construction of the device will be apcontinuous highfrequency oscillations in the grid circuit, without employing energyobtained from the plate circuit.

It is a further object of this invention to provide a tuned. circuit,resonant at high frequency, with a device by meansof which a lowfrequency modulation may be impressed thereon.

It is a further object of this invention to provide a modulating meanswhich employs only a Very small amount of energy and is capable ofproducing large changes in the radiated energy. p

Other objects of my invention and details parent from the followingdescription and the accompanying drawing in which:

Figure l is a diagram of circuits showing oneeform of my invention,

a modification of one shown in Fig. 1, Fig-1 is a like illustration ofanother m'odification of the same part, and

Fig. 2 isv a diagrammatic showing of circuits embodying anothermodification of my invention.

The vacuum tube device is provided with an anode 1 and a cathode 2. Abattery 3 and a resistance 4 constituting the usual arrangement forsupplying heating current to the filament or cathode 2.

, The plate circuit, which. connects the anode 1 and cathode 2, includesan inductance 6 by which it is coupled to the radiated circuit includingan antenna 5 and the ground connection. The plate circuit is suppliedwith energy'by a battery 7 which is shunted by a condenser 8 in theusual way. The vacuum tube is supplied with a grid 9 which is connectedto a circuit 10, tuned Fig. 1 is a diagrammatic illustration of part ofthe deviceinductive relation with the coil 12.-

Various means may be used for impress: ng low frequency potentialchanges upon the coil 13. One way of doing this is illustrated in Fig.1, in which the terminals 14 and 15 of this coil are connected. througha battery 16 and a microphone 17.

When sound is received on the microphone, current fluctuations aredeveloped in the circuit 1613 which causes a difference of potentialbetween theterminals of this coil and this potential difierence issuperposed upon the potential difference due to the high-frequencyoscillations in the circuit 10, both high-frequency and low-frequencychanges being impressed upon the grid 9. The energy of thehigh-frequency oscillations in the circuit 10 may, ifvdesired be reliedupon to supply :the current through the microphone 17, and the battery16 omitted.

The potential changes impressed upon the v grid 9 are amplified by thetube 1 and appear in the antenna circuit as modulated, highfrequencyoscillations. Since there is no coupling between the grid circuit 14 andthe plate circuit, no feed-backaction takes lace.-

It is not possible, therefore, for the tu e to obliterate the si ated bythe tube itself. Since there is no tort the signal by too close acoupling. The

potential changes at the terminals of the.

coil 13, need not be produced by a microphone.- Any desired way ofintroduci an audio-frequency variation ma be su stituted. In Fig. 1 abuzzer is s own instead of the microphone. The'buzzer' is provided alsby oscillations gener- 90 couplingto a'djust, it is not possible to dis,

' rent to pass readily.

generator is shown for impressingupon the coil 13,an audio frequencyvariation. Since the energy needed for this modulationis small, thealternating current generator may be driven by a small siren.

Instead of coil 13, a condenser may be used. This is illustrated in Fig.2 in which the resonant circuit 10 is tuned by means of the inductance12 and the adjustable condenser 11 and is energized from the coil 12orin any other desired way. The condenser 20 is insertedinthe circuit 10in a position corresponding to that of the coil 13. A second condenser19 is shown between the grid 9 and the connected point of the circuit10. Either of the condensers 19 and 20 may be omitted if desired. Inorder to provide an all-metallic path between the grid; 9 andthe cathode2, the connection by means of which the audio-frequency energy issupplied is joined to the high-frequency circuit at the grid side of thecondenser 19 and the cathode side of the condenserQO. In thisconnection, the secondary of a transformer 18 is included. The primaryof this transformer is supplied with audio-frequency energy in anydesired way; for example, by any of the'ineans described in connectionwith Fig. 1.

The condensers l9 and 20 are too small to pass audio-frequency currentbut are large enough to permit the radio-frequency cur- Consequently,,the audio-frequency potential difference upon opposite sides of thecondensers 19 and 20 is impressed upon the grid 9 without interferingwith the action of the high-frequency circuit 10. In the same way, thesecondary of the audio-frequency transformer 18 acts as a chokecoil,'preventirTg passage of the high-frequency oscillations, futconducting audio-frequency currents; Th circuit 10, therefore, is notdisturbed by the potentials on the condenser 20, but is tuned by meansof the adjustable condenser. 11 and carries continuous high-frequencyoscillations which are impressed, through the condenser 19, upon thegrid 9. The grid 9, therefore, carries both frequencies.

The act-ion of the righthand half of the device illustrated in Fig. 2 islike that described in connection with Fig. 1, amplifying the energyimpressed upon the grid 9 and sending out high-frequency radiations,modulated at an audio frequency. The absence of any coupling between theanode circuit and the grid circuit is as complete in the formillustratedin Fig. 2 as it is in the form illustrated in Fig. 1 and the resultingadvantages are the same.

Although I have illustrated and specifically described but a fewmodifications of my device, other variations will be apparent to thoseskilled in the art and the limited number of forms specificallydescribed is not to be regarded as a limitation. No limitation exceptthat necessitated by the prior art or indicated by the claims isintended.

I claim as my invention:

1. In a non regencrative, vacuum-tube amplifier including a grid, afilament and a plate, a grid circuit including a source ofradio-frequency and a tuning device co-operating therewith to rendersaid grid circuit resonant to said radio frequency, an allmetallicconnection between the grid and filament for removing grid charge andstopping condensers on each side of said source of radio frequencypreventing the grid charge from passing through said source of radiofrequency.

2. In a non-regenerative, vacuum-tube amplifier including a grid, afilament and a plate, a grid circuit including a source ofradio-frequenc and a tuning device co-operating therewit to render saidgrid circuit resonant to said radio frequency, an allmetallic connectionbetween 'the grid and filament for removing grid charge, saidallmetallic connection including a source of audio frequency andstopping condensers on each side of said source of radio frequencypreventing the grid charge from passing through said source of radiofrequency, said source of audio-frequency together with said stoppingcondensers presenting a high impedanceto the radio frequency Intestimony whereof I affir my signature.

DR. 1G: LUDv 'IG Kt'HN.

